28mm and 35mm are very common focal lengths in the olden days. Partly because these are comfortable focal lengths for most people. Anything wider and it becomes difficult to control. Also, they are relatively easy and cheap to make, for most of them.
For the 28mm, my favourite is the Leica-R 28mm f2.8 Elmarit. As with all Leica lenses, it's very well made. The only concern I have with this lens, is that one version of it has the pins on the lens where the hood attaches to, and these two pins are easy to become loose and comes off with use. I had one like that, and the hood can no longer be attached. The do not remove the hood on the one I have now. The lens is optically very good and I love the colours from this lens. The only complain about it is the pretty severe vignette wide open. The other favourite 28mm is the Pentax original K-Mount 28mm f3.5, whose design was derived from the famous and popular Takumar 28mm f3.5. Compact and sharp, and focuses so smoothly that in itself, is a joy.
The 35mm focal length is a bit tough, simply because I have so many of them and I also like many of them. I wrote about them here before, and I will reuse the picture below:
My favourite is still the Leica-R 35mm f2. This is a lens that never fails me in giving me pictures that I like. The colour and contrast of this lens is so pleasing to my eyes. The other 35mm lenses I like a lot is the Minolta MC 35mm f1.8 and the Olympus 35mm f2, in that order. I kind of regretted selling the MC 35mm f1.8. Really should have kept it. In the list above, I still have all of them except the Nikon 35mm f1.4. I got rid of it since I didn't like it much. The first lens on the list is the Takumar SMC 35mm f2 which I traded for the OM 35mm f2 from Adam. I like the OM better than the Tak, although the Takumar 35/2 is harder to find.
There are so many fine lenses in the 28mm and 35mm that are very good. If you just started with manual focus lenses, I would suggest something cheap, like a Vivitar, Soligor, Minolta or even some less known third party marque like Makinon, which sells next to nothing, but many of them are surprisingly good.